An electromagnetic pilot type directional control valve configured to drive a spool that slides within a valve aperture for switching flow channel by one or two electromagnetically operated pilot valves is known in the related art. In the directional control valves of this type, the pilot valve is mounted to one or both ends of the housing in the axial direction or on a top surface of the housing. The directional control valve having a pilot valve on the top surface of the housing as in the latter case has an advantage such that the widthwise length can be reduced, and hence is suitable to be used in a space which is narrow in width.
Patent Document 1 discloses a directional control valve having a pilot valve mounted on a top surface of housing. This directional control valve has the pilot valve covered by a protective cover, and is superior in waterproof property, and hence there is no specific problem in terms of function. However, since the pilot valve is mounted directly on the top surface thereof, a plurality of pilot flow channels that extend in the interlacing directions with respect to each other must be formed in the housing along selected routes while being bent where needed in order to avoid mutual intersection. In addition, a plurality of screw holes for mounting the pilot valve must also be formed at positions where interference with the pilot flow channels is avoided. Therefore, there is a slight difficulty in workability.
What is generally required for the directional control valve of this type is that parts such as a pilot valve and a printed circuit board related thereto are assembled compactly and efficiently to the housing. It is also important that those parts can be dismounted easily from the housing in sequence and mounted easily again to the housing in sequence.
Japanese Unexamined Patent Application Publication No. 8-145230